Subtitling realized by rendering graphics streams is an important technique for allowing people in different linguistic areas to appreciate a film produced in a language other than their native languages. An example of a conventional technique of subtitling is a memory allocation scheme for a Pixel Buffer based on the ETSI EN 300 743 standard set forth by European Telecommunications Standards Institute (ETSI). The Pixel Buffer is a memory for temporarily storing decompressed graphics, and a reproduction apparatus writes the graphics in the Pixel Buffer to a display memory called a Graphics Plane, and thus the graphics is displayed. In the memory allocation scheme, a definition of a Region is included in the Pixel Buffer, and a part of the decompressed graphics that corresponds to the Region is written to the Graphics Plane. For example, when a subtitle “Goodbye . . . ” is contained in the Pixel Buffer and a position and a size of the Region are defined so as to includes a part “Go”, then the part “Go” is written to the Graphics Plane and displayed on the screen. Likewise, when the position and size of the Region are defined so as to includes a part “Good”, then the part “Good” is displayed on the screen.
By repeating of the defining of the Region and the writing to the Graphics Plane, the subtitle “Goodbye . . . ” is displayed on the screen gradually, i.e., first “Go”, next “Good”, then “Goodbye”, and finally the whole subtitle “Goodbye . . . ” is displayed. By rendering a subtitle in such a way, it is possible to realize a wipe-in effect.
The ETSI EN 300 743 standard, however, does not at all consider to guarantee the sync between a graphics display and a picture display when a burden for writing to the Graphics Plane is high. The graphics written to the Graphics Plane is not compressed, and accordingly, the burden for writing to the Graphics Plane increases as a resolution of the graphics becomes higher. A size of the graphics to be written to the Graphics Plane is up to 2 Mbytes when rendering the graphics in a resolution of 1920×1080, which is a proposed standard resolution for a BD-ROM, and a higher bandwidth for a graphics data transfer from the Pixel Buffer to the Graphics Plane is necessary in order to render graphics as large as 2 Mbytes synchronously with the picture display. However, demanding a high bandwidth for the data transfer to write the graphics to the Graphics Plane hinders an attempt of cost reduction in manufacturing the reproduction apparatus. It is possible to lower the necessary bandwidth in writing to the Graphics Plane by having the reproduction apparatus always perform a “reasonable write”, in which only a difference from a previous display is written to the Graphics Plane. However, demanding the reproduction apparatus to always perform the “reasonable write” restricts software applicable to the reproduction apparatus.
As described in the above, the high burden for writing to the Graphics Plane demands that reproduction apparatuses operate in the high bandwidth or perform the reasonable write, and as a result, restricts product development of reproduction apparatuses.